Meteor Activity Outlook for July 30-August 5, 2011

During this period the moon reaches its new phase on Saturday July 30th. At this
time the moon will lie near the sun and will not be visible at night. Next week
the waxing crescent moon will enter the evening sky but will not cause any
interference to observers as it will set long before the active morning hours
arrive. This period will be the best time to view meteor activity during July
and August as the Perseids will suffer from a full moon at the time of their
maximum. The estimated total hourly rates for evening observers this week is
near six as seen from the northern hemisphere and seven as seen from the
southern hemisphere. For morning observers the estimated total hourly rates
should be near thirty no matter your location. The actual rates will also depend
on factors such as personal light and motion perception, local weather
conditions, alertness and experience in watching meteor activity.

The radiant (the area of the sky where meteors appear
to shoot from) positions and rates listed below are exact for Saturday night/Sunday
morning July 30/31. These positions do not change greatly day to day so the
listed coordinates may be used during this entire period. Most star atlases
(available at science stores and planetariums) will provide maps with grid lines
of the celestial coordinates so that you may find out exactly where these positions
are located in the sky. A planisphere or computer planetarium program is also
useful in showing the sky at any time of night on any date of the year. Activity
from each radiant is best seen when it is positioned highest in the sky, either
due north or south along the meridian, depending on your latitude. It must be
remembered that meteor activity is rarely seen at the radiant position. Rather
they shoot outwards from the radiant so it is best to center your field of view
so that the radiant lies at the edge and not the center. Viewing there will allow
you to easily trace the path of each meteor back to the radiant (if it is a shower
member) or in another direction if it is a sporadic. Meteor activity is not seen
from radiants that are located below the horizon. The positions below are listed
in a west to east manner in order of right ascension (celestial longitude). The
positions listed first are located further west therefore are accessible earlier
in the night while those listed further down the list rise later in the night.

The following showers are expected to be active this week:

The Alpha Capricornids (CAP) are active from a wide radiant located at 20:22
(306) -10. This position lies in northwestern Capricornus, two degrees north of
the third magnitude double star Alpha Capricornii. The radiant is best placed
near 0100 local daylight time (LDT), when it lies on the meridian and is highest
in the sky. Current rates should be near two per hour as seen from the northern
hemisphere and three per hour from the southern. Maximum activity occurs on July
30th. Don’t confuse these meteors with the antihelion meteors, which have a
radiant just to the east. Both radiants need to be in your field of view to
properly sort these meteors. With an entry velocity of 25 km/sec., most activity
from this radiant would be slow, a bit slower than the antihelions. This radiant
is well seen except for far northern latitudes where it remains twilight all
night long and the radiant does not rise as high into their sky.

The wide Antihelion (ANT) radiant is now centered at 21:20 (320) -14. This area
of the sky lies on the border of Capricornus and Aquarius, three degrees north
of the fourth magnitude star Iota Capricorni. This radiant is best placed near
0200 LDT, when it lies on the meridian and is located highest in the sky. Due to
the large size of this radiant, any meteor radiating from Capricornus, western
Aquarius, eastern Aquila, or northern Microscopium could be a candidate for this
shower. Rates at this time should be near one per hour as seen from the northern
hemisphere and two per hour as seen from south of the equator. With an entry
velocity of 30 km/sec., the average Antihelion meteor would be of medium-slow
speed.

The Delta Aquariids (SDA) will reach maximum activity on Saturday July 30th.
Hourly rates will depend on your latitude. Those viewing from the southern
tropics will see the highest rates of near 15 per hour. Rates seen from
mid-northern latitudes will range from 5-10 per hour, depending on the haziness
of your skies. The radiant is currently located at 22:45 (341) -16. This
position lies in southwestern Aquarius, two degrees west of the third magnitude
star Delta Aquarii. The radiant rises near 2200 (10pm) LDT for observers located
in the mid northern latitudes, but is best placed near 0300 LDT, when it lies
highest in the sky. With an entry velocity of 42 km/sec., most activity from
this radiant would be of average velocities.

The Piscids Austrinids (PAU) are a minor shower not well seen from the northern
hemisphere. This radiant is active from July 15 through August 10. Maximum
activity occurred on July 28 when the zenith hourly rate (ZHR) may reach five.
These rates are only seen from the southern hemisphere where the radiant passes
overhead. From mid-northern latitudes, rates of one per hour at maximum are
usually seen. The radiant is currently located at 22:56 (344) -29. This position
lies in eastern Piscis Austrinus, very close to the bright first magnitude star
Fomalhaut (Alpha Piscis Austrinus). The radiant is best placed near 0300 LDT,
when it lies highest in the sky. With an entry velocity of 35km/sec., most
activity from this radiant would be of average velocities.

Studies by Sirko Molau and Juergen Rendtel of the IMO’s video data have revealed
an active radiant in the constellation of Pisces this time of year. The August
Piscids (AUP) are active from August 2nd through the 9th with maximum activity
occurring on the 4th. On the 4th, the radiant is located at 00:30 (008) +18.
This area of the sky lies in north-central Pisces, five degrees northeast of the
second magnitude star Algenib (Gamma Pegasi). Interestingly, if one were to
continue the radiant drift for the July Pegasids into August, it would closely
match that of the August Piscids. This radiant is best placed during the last
dark hour before dawn, when it lies highest above the horizon in a dark sky.
Rates at this time should be less than one no matter your location. With an
entry velocity of 66 km/sec., the average August Piscid meteor would be of swift
speed.

The Perseids (PER) are active from a radiant located at 01:58 (029) +54. This
position lies in western Perseus, twelve degrees north of the famous second
magnitude double star Almach (Gamma Andromedae). The radiant also forms an
equilateral triangle with Almach and Mirfak (Alpha Persei). The radiant is best
placed during the last hour before the start of morning twilight when it lies
highest in a dark sky. Current rates would be 3-5 per hour at best, as seen from
the northern hemisphere. Activity from this source is poorly seen from the
southern hemisphere and not visible at all south of 40 degrees south latitude.
This shower does not peak until August 13, and the bright moon will spoil the
show. With an entry velocity of 61 km/sec., most activity from this radiant
would be swift.

As seen from the mid-northern hemisphere (45N) one would expect to see
approximately twelve sporadic meteors per hour during the last hour before dawn
as seen from rural observing sites. Evening rates would be near three per hour.
As seen from the mid-southern hemisphere (45S), morning rates would be near
seven per hour as seen from rural observing sites and two per hour during the
evening hours. Locations between these two extremes would see activity between
the listed figures.

The table below presents a condensed version of the expected activity this week.
Rates and positions are exact for Saturday night/Sunday morning.